Taking of dental impressions



O 30, 1 J. SCHREINEMAKERS 3,060,578

TAKING OF DENTAL IMPRESSIONS Filed May 5, 1959 United This invention relates to dental techniques and, more particularly, to implements for taking impressions of a toothless lower jaw for the purpose 'of producing a prothesis or denture.

Various methods are known for the production of dentures. The simplest method is the socalled symmetrical process in which a denture is made with the aid of a model obtained by means of an impression. With this method, there is the disadvantage that both the anatomy of the mouth and the action of the muscles surrounding the jaw are not sufficiently taken into account, resulting in a denture being obtained which does not fit as well as it should.

Better results are obtained, when a socalled anatomical impression of the jaw is taken, where all details capable of anatomical study are reproduced in the impression and are worked up in the denture. However, even with this method, the influence of the musclar action referred to is not considered, which detrimentally affects the results obtained.

For overcoming these disadvantages, another known method of producing a denture is based on a so-called functional impression, in which the muscles surrounding the jaw are set in motion during the taking of the impression. At the side of the bottom of the mouth, however, difficulties are encountered, and dentures made according to this method generally do not fit satisfactorily, as insuflicient suction between the denture and the bottom of the mouth is established.

For obaining better results as regards this detail, it is possible, according to another known method, to start from a suction-producing functional impression. This method, however, takes much time and is complicated and is based on an unnatural position of the tongue which is raised by a thick roll placed in the associated sublingual space.

In the denture made by this method, it is necessary first of all to produce a situation impression, whereupon an individual tray-shaped implement is made. This individual tray is lined in the sublingual space with molding material to a thickness of about 6 mm., whereby the tongue, as mentioned above, is raised out of the bottom of the mouth. By means of the contact thus produced, a suction effect is brought about between the bottom jaw and the tray. Because, however, with the denture made in this manner, a check in the functioning of the musculusgenio-glossus will generally occur, this suction effect will be mostly rendered ineffective again by subsequently effected corrections.

An object of the invention is to remove the disadvantages attaching to the aforesaid methods and to make available a factory-made tray for obtaining an impression on a toothless lower jaw, with which a really well fitting denture can be made in a very rapid manner.

For this purpose, the tray according to the invention is characterized by the feature that the breadth, depth and length of its lingual part bear such a relation to the jaw that, during the taking of an impression in the lingual part of the mouth with the tongue protruding, a uniform pressure is exerted on the bottom of the mouth.

With any known tray, it is impossible to exert a uniform pressure on the bottom of the mouth with the lingual part of the tray, as its shape is not suitable for the purpose. If this condition be corrected, however, it becomes tates atent 2 possible with such a tray to obtain in one opeartion an impression which enables a suction-producing denture to be made, while maintaining the proper functioning of the tongue, as is the case with the tray according to the invention. Consequently, it becomes possible, when using factory-made trays, to obtain in one operation and without the use of an individual tray, a suctionsproducing denture.

Trays are intended to obtain an impression of the jaw with such a shape as to allow for as uniform as possible a thickness of the impression compound in the tray. These trays also sometimes serve the further purpose of transmitting the influence of the muscular action at the cheek and lip side of the jaw to the impression. The influence of the muscular action at the bottom side of the mouth, however, receives no attention or only liimted attention in commercially obtainable trays.

With trays provided according to the invention, however, the functional process at the lingual side of the jaw is regarded as primary without, however, neglecting the further part of the jaw. Thus, while the functioning of the tongue is maintained, a perfectly satisfactory suction for the finished denture is obtained and maintained. The denture is so shaped that the action of the muscle groups, with which the denture comes in direct or indirect contact, can be maintained without the suction effect of the denture being thereby afiected.

A satisfactory construction of a tray, in which in the region of the musculus-genio-glossus there is provided a recess in the lingual edge of the tray, is characterized according to the invention in that this recess is so formed that, in taking an impression with the tongue extended, a uniform tension will be provided between the impression rim and the mucus membrane covering the musculusgenio-glossus with the part adjoining. Further, the lingual tray-rim, up to where the greatest mass of the glandula sublingualis lies, runs slightly divergent to the linea mylohyoidea and overreaches the action limit from the processus alveolaris onwards. The pad, when the lingual rim in the forward region covers the musculus-genioglossus at a distance of 1 to 2 mm. from the jaw, is received wholly or in part in the tray.

The bottom of the mouth adjoining the jaw is subdivided into regions reacting in two different ways, namely into parts of the mucus membrane in the bottom of the month, which are moved directly by the muscles lying under them, and also into regions which move indirectly under the influence of muscular action, there being a gland texture between the muscle and the mucus membrane of the mouth. The latter regions are of course more impressionable when pressure is applied, as the gland texture is more or less displaceable, the measure of this impressibility being related to the character of the gland texture which is present. Between the musculusmylo-hyoideus and the musculus-genio-glossus, there will occur during the function a far reaching synchronization. The musculus-genio-glossus can in practice never be active Without the musculus-mylo-hyoideus being operative, as the latter muscles function is to fix the tongue bone for the action of the lingual muscles. 7

For obtaining a denture with a suction action, a certain tension mus-t be extred over the entire edge of the denture. For this purpose, it is necessary to produce in the bottom of the mouth a certain tension between the denture rim and the mucus membrane in the bottom of the mouth. This tension must be evenly distributed during the tongue action over the entire rim, in order that the greatest possible tongue function shall be obtained, because a nonuniform tension influences the pressure on the muscles or muscle attachments directly or indirectly in such a manner as to cause a check on the action of the tongue.

As has already been stated above, at each action of the tongue both the musculus-genio-glossus and the musculusmylo-hyoideus become almost simultaneously active as regards their function, a tension at the places of insertion of course occurring. The effect of these muscles will thus be observable at the bottom of the mouth more or less in accordance with the run of the insertion places, the measure of the local muscle development, however, also having an effect. For the musculus-mylo-hyoideus this effect occurs on a line ascending from front to back along the jaw, the linea-mylo-hyoidea, so that, as already stated, the lingual tray rim extends to the point of greatest mass of the glandula-sub-lingualis slightly divergent to these linea and overreaches the limit of action starting from the processus alveolaris.

As the lingual tray rim runs slightly divergent to the linea-mylo-hyoidea, a uniform tension between the tray rim and the mucus membrane of the bottom of the mouth is obtained, which in this case is directly influenced by the musculus-mylo-hyoideus.

By the term action limit, a limit or line around the jaw is understood which indicates the region up to which the mucus membrane of the bottom of the mouth moves in harmony with the efifect of the muscle. The adhesion of the muscle groups never lies at this limit, but always at some distance from it. For the purpose of bringing about a certain tension between the denture and the surrounding textures, it is necessary to overreach the action limit from the processus alveolaris.

In addition, there is produced in the region of the musculus-genio-glossus a vertical recess in the lingual rim of the tray such that, with the tongue extended, a uniform tension between the edge of the impression and the mucus membrane covering the musculus-genio-glossus with the adjoining part belonging to it is created.

Immediately behind the frontal part of the jaw in the lingual region lie the draining ducts of the glandula-sublingualis. These draining ducts must be left clear during the taking of the impression, as a covering up of them would result in a swelling of the bottom of the mouth. For this purpose, the lingual rim in the front region covers the musculus-genio-glossus at a distance of almost 2 mm. A minimum distance of 1 mm. is necessary for insuring a minimum thickness for the impression compound.

With advantage, a constructional form of the tray according to the invention can be employed, which is characterized by the feature that the distance between the lingual rim and the jaw is almost constant.

The invention shall now be described with reference to the drawings which illustrate a constructional example of the invention, several details which may be used with advantage being especially shown.

FIG. 1 shows in perspective a spoon-like element according to the invention for taking an impression on a toothless lower jaw.

FIG. 2 shows in perspective, how the measurement is taken in the mouth with the aid of a compass-like implement; and

FIG. 3 shows in perspective how the measurement of a spoon is taken with the aid of the compass-like implement.

In the constructional form of the spoon according to the invention, shown in FIG. 1, 1 indicates the lingual tray rim and 2 the buccal tray rim. 3 is the vertical recess in the lingual edge for the musculus-genio-glossus, while the part of the lingual tray rim, which runs slightly divergent with respect to the linea-mylo-hyoidea is designated by numeral 4. It will be clearly seen that the lingual marginal part 5 lying between 3 and 4 runs upwards in the region of the glandula-sub-lingualis following a gently curved line on both sides.

The part of the buccal rim in the masseter region is indicated by 6, while 7 indicates the triangular recess for the buccal frenulum.

8 indicates the part of the tray covering the crown of the processus, while 9 indicates the part of the tray, which in situ bears wholly or in part on the trigonum retromolar pad. Finally, 10 indicates the tray handle, the height of which substantially corresponds to the height of the teeth to be arranged in the denture, while 11 indicates a finger support.

The trays according to the invention are made in series so that a fitting impression can be obtained despite the greatest variation of jaws.

For the purpose of manufacturing these trays, there will first be selected from a great number of jaws a series of jaw prototypes, on which the trays are to be made, which selection will be made in such a manner that with the finally obtained series of trays a correct impression can be taken from all jaws likely to exist. The jaws 12 are selected with the aid of a compass arrangement 13 con structed for this purpose (FIG. 2), the ends 14 of which enclose with the legs 15 such an angle that the ends 14 are almost parallel, when their distance from each other is 3 /2 to 5 /2 cm. Furthermore, the ends 14 are so reduced in thickness that their total thickness amounts to about 2 to 4 mm.

When selecting the jaws, the distance between the pads 16 is determined by bringing the outsides of the compass ends 1 into contact with the parts of the pad lying nearest the center line. As has been found, this distance lies in general, even in the most varied jaws, between 3 /2 cm. and 5 /2 cm., and by the selected construction of the compass ends 14, these ends, when in the measuring position, will generally be brought approximately to parallel positions, whereby the measuring results will be advantageously influenced.

Through these measurements, the jaws are subdivided into groups having the same distance between pads. From numerous measurements of this kind, it has been found unexpectedly that this distance is practically determinative for the whole of the jaw shape, so that from jaws, in which the pad distances measured by the compasses entirely or almost entirely agree, an impres sion can be taken with the same tray.

For the series of the trays to be manufactured, a start is thus made, according to the invention, from jaws with different distance between the pads, such that through this selected series of jaws, the entire range of distances between the pads, lying as stated above between 3% cm. and 5 /2 cm. is generally uniformly distributed.

For manufacturing a tray according to the invention with a jaw selected in such a manner as the starting point, a suitable tray of one of the known constructions is used, the musculus-genio-glossus being fully exposed through the material of the tray being removed at this place (that is at 3). In addition, the tray rim is made short on the lingual side and at the same time ascending an an inclination backwards and material is removed at the back in accordance with the run of the linea-mylo-hyoidea viewed from the lingual side (part 4). In the region of the masseter (part 6), the tray is cut away in such a manner that the action of the masseter is not interfered with by the tray. Then, with the tongue extruded, an impression is taken with stents or some similar impression material, whereupon the constructional material is applied to the edge of the impression in the sublingual region, namely from P on the left to P on the right. Consequently, the impression is built up slowly on the lingual side in the vertical sense and regularly hardened, the tongue remaining extruded as long as the impression is in situ. In this way, an impression is obtained, in which the extent of the sublingual region is so formed at the edges that the tongue can be extruded without obstruction, while the impression formed nevertheless offers resistance at the front side to upwardly directed pressure.

Thereupon, with the tongue still extruded and while using material which, while being applied in the mouth, offers during the muscular action a certain resistance to the pressure of the bottom of the mouth, the same edge formation is carried out for the region where the tray rim comes into contact with the mucus membrane, which is under the direct influence of the musculus-mylo-hyoideus. Of course, care must be taken to prevent any change of the impression during this work in the sublingual region.

Furthermore, the tray used is lengthened in such a manner that it will entirely or partly cover the retromolar pad (part 9 of FIG. 1).

In the buccal region at the level of the masseter, the obtained impression is softened at the buccal rim, so as to fix the limit of the range of action of the masseter in the impression. This is effected through the impression, after the edge in question has been softened, being again placed in situ, whereupon the patient is caused to tension the masseter by exerting a counter pressure on the tray. The tray may extend on the buccal side into the region of the masseter as far as the masseter (part 6 in FIG. 1). The remaining labial and buccal part of the rim is, after being softened, conformed by massage applied to the cheeks and lips over the impression.

From the impression of the jaw, with the bottom of the mouth and buccal and labial parts obtained in the above manner, a model is thereupon made. This model is lined with wax or some similar material in such a manner that a mold is obtained, which covers all mouths of the group belonging to the tray to be made. For this purpose, the pad part is covered with only a small amount of material, for instance with a wax plate having a thickness of about 1 mm., in such a manner that the end of tray follows a course which, with the exception of the outermost edge, is not oppositely directed to the course of the pterigo-mandibular connection. Sublingually, the model is built out in the region of the front side with a wax plate thickness of about 1 mm. in the horizontal sense in the socalled impression rim. In the rounding of this rim at the level of the molars this thickness is about doubled and maintained towards the back, whereupon at the level of the retromolar pad, it is again reduced to about 1 mm. Any unevennesses in the course of the lingual processus edge in the direction of the jaw are entirely filled with modelling material.

In this way is developed, on the lingual side, a mold which has in the impression edge a certain uniform thickness in relation to the jaw and which as regards the group of the jaws to be treated with a certain tray leaves a tolerance as regards the size of this form and neverthless insures a more or less even thickness of the impression material in the tray.

Medially, as well as regards the retromolar pad, only a small amount of material is used in the lingual region, but so much that the tray to be made on this model is slightly undercut from the pad to the lingual rim of the impres- $1011.

From the above-mentioned lingual part of the model, the processus part is built-up with modelling material to such a height that practically every processus of the jaw group in question can be accommodated in the model, when the model lies horizontally at the height at which the retromolar pad merges into the processus-alveolaris. By the term horizontal position of the model is to be understood that the lower surface of the model runs practically parallel to the greatest part of the processusalveolaris. From the highest point of the processus part of the modelled initial jaw, the under surface of the tray inclines towards the cheek side at an angle to the buccal In the labial region, the same steps are taken as in the buccal region. The final thickness of the edges of the tray lies between 1 mm. and 3 /2 mm., in order that during the production of a tension between the tray and the bottom of the mouth, any damage to the latter will be prevented.

The trays constructed in this manner can thus bear with their rear ends 9 on the pads and rest in the bottom part of the mouth as far as the impression edge on the model, While the distance from the edge to the jaw is kept lingually as small as possible. The processus-alveolaris and the buccal and lingual turn-over fold have plenty of space as regards the tray so that, on the insertion of the tray into the mouth and on a light pressure being exerted on the finger supports 11 provided on the tray, 21 light, very uniformly distributed tension is exerted by the lingual rim of the tray on to the bottom of the mouth.

Moreover, the lingually lying mucus membrane which covers the jaw and which may have folds, which frequently occurs especially in resorbed jaws, is smoothed down so that a beautiful and faultless impression of the jaw is obtained.

Bucally and lingually, the tray reaches to the masseter, the cheeks and the lips and, due to its form, allows of a flow of the impression material right into the fold when the cheeks and the lips are at rest. In the rim of the tray, small triangular recesses 7 are provided at the level of the frenuli. The entire tra-y rim must be free from sharp corners and run smoothly.

Owing to the circumstances that the level of the tray handle corresponds practically to the level of the teeth to be fixed in the denture, the extruded tongue which, during the taking of the impression rests on the handle 10, will encounter the same resistance which is normally reached when the tongue is stuck out in the toothed jaw.

In the'manner described, there is produced from the series of selected initial jaws a series of trays, which correspond markedly in their shape, especially in the lingual region and around the pad and with which, in one operation, an impression can be taken of all ordinarily existing jaws, which is required for the production of suction producing dentures.

From the methods of selecting the initial jaw 12 with the aid of compasses 13 (FIG. 2) follows a very simple method for selecting the correct spoon for any particular aw.

In the manner shown in FIG. 2, there is first of all measured with the compasses 13 the distance between the pads of the jaw, whereupon with the aid of the compasses 13 the correct tray is selected, for which purpose the compass ends :14 must come into contact with the lingual part 9 of the inner side of the spoon to be used (FIG. 3). If required, a scale may be provided on the compasses from which, when taking the measurement, the correct number of the tray to be used can be read off directly.

As already stated, the total thickness of the ends 14 of the compasses 13 lies between 2 and 4 mm., so that between the tray and the jaw sufiicient space remains for the impression-receiving compound since, when measuring the jaw, the outer surface, but when measuring the tray, the inner surface of the compasses ends 14 is used as the measuring planes.

By factory made trays are to be understood in this specification, trays which are made by mass production in a manner similar to trays which are now commercially obtainable.

The invention is not confined to the constructional example illustrated in the drawings, which may be varied in many ways within the limits of the invention.

What I claim is:

1. A factory made implement for taking impressions on a toothless lower jaw comprising a tray including portions correlated with the human mouth and a lingual part, said lingual part in the region corresponding to the musculus-genio-glossus being provided with a vertical recess, said recess having a shape such that, during the taking of an impression with the tongue extended, a uniform tension is exerted between the impression rim and the mucus membrane covering the musculus-genioglossus, the lingual part including a rim extending to a position corresponding to the region of the greatest mass of the glandula sublingualis in the mouth, said rim of the lingual part extending slightly divergent to the linea-mylo hyoidea and overreaching the action limit at the processus alveolaris, and with the lingual rim in the forward region 7 covering the musculus-genio-glossus at a distance of between about 1 to 2 mm. from the jaw, the retromolar pad being received at least in part into the tray.

2. An implement as claimed in claim 1, wherein the lingual rim in the region of the glandula-sublingualis is inclinded upwardly and follows a curved line whereby when the musculus-genio-glossus and the musculus-myld hyoideus are active, the tray exerts in this region a uniform pressure during the taking of the impression.

3. An implement as claimed in claim 1, comprising a portion of the tray for covering the crown of the processus, the latter said portion lying approximately in a given plane, said tray including a further portion adjoining the last said portion, said further portion in situ bearing against the retromolar pad, and extending 8 obliquely upward and backward with respect to said plane.

References Cited in the file of this patent UNITED STATES PATENTS 279,460 Tetley June 12, 1883 1,835,674 Short Dec. 8, 1931 2,696,668 Fox Dec. 14, 1954 2,848,811 Wagner Aug. 26, 1958 FOREIGN PATENTS 1,147,995 France June 17, 1957 1,154,228 France Oct. 28, 1957 1,037,866 France May 6, 1953 

